Shock wave generators are used in numerous medical fields. The best-known field is the therapeutic and cosmetic application in the treatment for instance of calculous diseases (e.g., urolithiasis, cholelithiasis) and the treatment of scars in human and veterinary medicine.
New fields of application relate to dental treatment, the treatment of arthrosis, the ablation of calcerous deposits (e.g., tendinosis calcarea), the treatment of chronic tennis or golfer elbows (so called radial or ulnar epicondylopathy), of chronic discomfort of the shoulder tendons (so called enthesopathy of the rotator cuff), and of chronic irritation of the Achilles tendon (so called achillodynia).
Furthermore, the generation of shock waves is used in the therapy of osteoporosis, periodontosis, non-healing bone fractures (so called pseudoarthrosis), bone necrosis, and similar diseases. Newer trials investigate the application in stem cell therapy.
Furthermore, the generation of shock waves can be used to exert mechanical stress, e.g., in the form of shearing forces, on cells, wherein their apoptosis is initiated. This happens for example by means of an initiation of the ‘death receptor pathway’ and/or the cytochrome c-pathway and/or a caspase cascade.
The term apoptosis is understood to refer to the initiation of a genetically controlled program, which leads to the ‘cell suicide’ of individual cells in the tissue structure. As a result, the cells concerned and their organoids shrink and disintegrate into fragments, the so-called apoptotic bodies. These are phagocytized afterwards by macrophages and/or adjoining cells. Consequently, the apoptosis constitutes a non-necrotic cell death without inflammatory reactions.
Therefore, the application of shock waves is beneficial in all cases, where it relates to the treatment of diseases with an abased rate of apoptosis, e.g., treatment of tumors or viral diseases.
Additionally, the generation of shock waves can be applied beneficially in the treatment of necrotically changed areas or structures in muscle tissue, especially in tissue of the cardiac muscle, in the stimulation of cartilage assembly in arthritic joint diseases, in the initiation of the differentiation of embryonic or adult stem cells in vivo and in vitro in relation to the surrounding cell structure, in the treatment of tissue weakness, especially of cellulitis, and in the degradation of adipose cells, as well as the activation of growth factors, especially TGF-[beta].
Likewise, the generation of shock waves can be used for avoiding the formation and/or extension of edema, for degradation of edema, for the treatment of ischaemia, rheumatism, diseases of joints, jaw bone (periodontosis), cardiologic diseases and myocardial infarcts, pareses (paralyses), neuritis, paraplegia, arthrosis, arthritis, for the prevention of scar formation, for the treatment of scar formation respectively nerve scarring, for the treatment of achillobursitis and other bone necroses.
Another application relates to the treatment of spinal cord and nerve lesions, for example spinal cord lesions accompanied by the formation of edema.
Shock waves are also applicable for the treatment of scarred tendon and ligament tissue as well as badly healing open wounds.
Such badly healing open wounds and boils are called ulcus or also ulceration. They are a destruction of the surface by tissue disintegration at the dermis and/or mucosa. Depending on what tissue fractions are affected, surfacial lesions are called exfoliation (only epidermis affected) or excoriation (epidermis and corium affected).
Open wounds that can be treated with shock waves comprise especially chronic leg ulcers, hypertensive ischaemic ulcers, varicose ulcers or ulcus terebrans due to a thereby caused improved healing process.
Furthermore, shock waves are suitable for the stimulation of cell proliferation and the differentiation of stem cells.
Typical shock wave generators comprise a basis device, to which a therapy head can be connected. The therapy head comprises an integrated reflector with a shock wave source and a coupling membrane.
The therapy head can be made from different materials and must comply with further safety requirement depending on the type of shock source.
The therapy head comprises a connection cable for connecting to a basis device. For the user, the therapy head represents a single unit.
Typically, the therapy heads at the devices are changeable, on the one hand to be able to attach different therapy heads or to be able to detach the therapy head for maintenance or refurbishing work.
The reflector, which is integrated in the therapy head, is at least partially filled with a liquid. The liquid usually comprises a wave impedance corresponding approximately to the wave impedance of the body to be treated. Thereby, an easy coupling of the shock wave into the target object is made possible and losses during the coupling are minimized.
For filling the reflector with liquid or for emptying the liquid the therapy head can comprise valves.
The shock source is typically located in a focus or relatively near to a focus of the reflector.
The shock source is connected to the basis device by a suitable connection via the reflector retainer. The basis device supplies the treatment head with the necessary energy. Depending on the device, the basis device is also counting the number of shocks.
For example, the shock source is a spark discharge section formed by two opposite pointed electrodes. When a voltage (usually in the order of magnitude of about 10 kV to about 30 kV) is applied to these electrodes and the distance between the electrodes is not too large, an electrical breakdown occurs in form of a spark discharge. The latency time, i.e. the time between applying the voltage and the electrical breakdown depends, amongst other things, on the distance of the electrode tips. By wearout of the electrode tips during spark discharge this distance increases with time. If the distance is too large, the breakdown is becoming more and more unreliable until it is no more possible.
EP 0 781 447 B1 describes that conducting, semiconducting, or polarizable particles with a diameter from preferably between a few microns to a few hundred microns are added to the liquid in the reflector, which allow a electrical breakdown between the electrodes even when the distance between the electrode tips becomes so large that no discharge would occur without these particles.
Spark discharge systems comprise so called catalyzer material in their filling which is intended to reduce the bubbles generated during the spark discharge. For example, the catalyzer material can comprise palladium oxide hydrate that can bind hydrogen generated by re-hydrogenation or permeated hydrogen. Since catalyzer materials predominantly are based on noble metals, they are extremely expensive.
The reflector usually is made from stainless steel materials or brass alloys to minimize corrosion of the reflector surface and, at the same time, to have a material as dense as possible at one's disposal, which, at the same time, reflects sound waves.